Tests are an invaluable tool for me and my team, I consider them to be a key piece of my engineering toolbelt that I’ve built up over the years. At Wayfair, teams use tests to maintain code quality, as a test-driven development tool, and as a way to self-document new features. All of this utility is possible when you have a set of tests, a “test suite”, which can be trusted; a test suite that works as advertised by producing consistent results.